The oculomotor system of rabbits and cats will be experimentally examined at two levels of analysis: Extraocular muscle and central nervous system. Cats will be reared under conditions of restricted binocular experience. Subsequently the stiffness of the eyes of the deprived cats will be measured under conditions in which the cats are unanesthetized. The cats will be sacrificed and histochemical techniques will be used to assay for mitochondrial density in extraocular muscles. The activity of cerebellar Purkinje cells in the flocculus of the unanesthetized rabbit will be recorded with microelectrodes, under conditions of vestibular and visual stimulation. The horizontal canals of another group of rabbits will be surgically destroyed. The effect of olivary cell activity and Purkinje cell activity in effecting compensation following vestibular damage will be examined. BIBLIOGRAPHIC REFERENCES: Barmack, N.H. Generation of force by rabbit extraocular muscles during vestibulo-ocular reflex. The Association for Research in Vision and Ophthalmology. Spring Meeting, Sarasota, Florida, p.54, 1975. Barmack, N.H. The potential dependence of the after-hyerpolarization of extraocular motoneurons. Fifth Annual Meeting of Society for Neuroscience, New York, 1975.